The present invention is generally related to power systems, and more particularly, is related to a power system using a multi-functional power interface unit that allows, among other things, for capturing electrical energy that otherwise would be lost in a system, such as a locomotive, etc.
Locomotives, due to various constraints such as cost, space, power interface compatibility, etc., generally do not have on-board energy storage, therefore the electrical energy that is produced during dynamic braking or in a self-load mode of operation is dissipated in large grids of resistors to maintain train speed during operation on down hill grades or during train deceleration. As suggested above, any viable installation of on-board storage in the locomotive needs to overcome the foregoing constraints in order to allow a locomotive manufacturer to provide a cost-effective and reliable solution to the needs of its customers and/or government regulators to supply even more energy-efficient locomotives. Thus, it would be desirable to provide a power system that uses a versatile power electronic interface and associated control capable of overcoming the foregoing constraints. For example, it would be desirable for the power interface unit to perform at least the following functions:
1). The interface unit should allow at least a portion of the energy that would be irretrievably lost in the standard dynamic brake (DB) grid resistors to be captured and utilized to operate, for example, electrical equipment generally powered through an auxiliary power bus of the locomotive. Examples of electrical equipment powered by the auxiliary may include motor loads, such as radiator fans, traction motor blower, alternator blower, air compressor, etc. It will thus be appreciated that this first function would allow for increasing the locomotive fuel economy while reducing engine emissions.
2). The same interface unit could further allow to be electrically reconnected, via suitable switches, along with appropriate software control, to provide excitation to a main traction alternator during cranking of the locomotive""s engine. This second function could allow to utilize the captured electrical energy to charge a suitable storage unit that in turn may be connected to power up the interface unit so as to excite the main traction alternator to provide mechanical power to the engine during an engine cranking mode of operation.
Generally speaking, one embodiment of the present invention fulfills the foregoing needs by providing a power system for a locomotive generally having an internal combustion engine coupled to drive a main alternator and an auxiliary alternator. The main alternator is coupled to power one or more traction motors and the auxiliary alternator is coupled to power predetermined electrical equipment. The system includes a main power bus generally powered by the main alternator. The system further includes an auxiliary power bus generally powered by the auxiliary alternator. A power interface unit is electrically coupled to the main power bus to capture and transfer electrical energy into the auxiliary power bus. The electrical energy may be generated during a predetermined mode of operation of the locomotive, such as during dynamic braking or self-load.
Another embodiment of the present invention further fulfills the foregoing needs by providing a power interface unit in a power system for a locomotive generally having an internal combustion engine coupled to drive a main alternator and an auxiliary alternator. The main alternator is coupled to power through a main power bus one or more traction motors and the auxiliary alternator is coupled to power through an auxiliary power bus predetermined electrical equipment. The power interface unit is electrically coupled to the main power bus to capture and transfer electrical energy into the auxiliary power bus. The electrical energy may be generated during a predetermined mode of operation of the locomotive. The power interface unit includes a voltage converter module selectively coupled to impart a desired voltage conversion to convert the voltage from the main power bus to the auxiliary power bus during selected modes of operation, including transfer of a portion of the power generated during dynamic braking. Power propagating between the main power bus and the auxiliary power bus allows the captured electrical energy to be utilized to operate the auxiliaries and/or stored in an energy storage device. An inverter module is selectively coupled in the interface unit to drive the main alternator during an engine cranking mode of operation.